材料期刊网

Crack Initiation under Cyclic Compression

FENG Meibin CHEN Xinzeng HE Jiawen 2nd Automobile Works , Shiyan , Hubei , China. Ningbo University , Ningbo , Zhenjiang , China. Xi'an Jiaotong University , Xi'an , China.

材料科学技术（英文）

The crack initiation behaviour under cyclic compression foy the notched specimen was investigated. It has been found that the cycles for crack initiation increase with the increase of compressive mean stress, and the decrease of stress amplitude. The stress amplitude plays a more important role than the mean stress does. Photoelastic coating and finite element methods were employed to measure and calculate the stress field in the notched part. The resul ts show that the crack initiation under compression is attributed to the tensile stress which may exist during unloadtng. If the true stress state in the notch is compressive, no crack initiates.

关键词: crack initiation , null , null

Introduction to atmospheric corrosion research in China

Science and Technology of Advanced Materials

In this paper, we introduce the research on atmospheric corrosion in China. We describe the climate characteristics and the classification of atmospheric corrosivity across the whole country. We also describe the rusting evolution under simulated wet/dry cyclic conditions. (C) 2007 NIMS and Elsevier Ltd. All rights reserved.

关键词: atmospheric corrosion;corrosivity;rusting evolution;weathering steels;rust;mechanism;so2;o-3;no2

R&D STATUS ON INTERMETALLICS IN CHINA

CHEN Guoliang(State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 , China)SHI Changxu (Academia Sinica , Beijing 100864 , China)

金属学报(英文版)

This paper briefiy introduces the R&D of intermetallics in China. R&D on intermetallics in a national scale in China began near ten years ago. The investigation in past years focused on the fundamental research and materials development. A significant progress has been made. Various components that made of Ti3Al Ni3Al, TiAl and Fe3Al have been successfully manufactured Some of them have been evaluted. It is expected that some intermetallic alloys will be produced in an industrial scale in the near future.

关键词: :intermetallic alloys , null , null , null

Key R&D activities for development of new types of wrought magnesium alloys in China

Transactions of Nonferrous Metals Society of China

Many researchers in China are actively engaged in the development of new types of wrought magnesium alloys with low cost or with high-performances and novel plastic processing technologies. The research activities are funded primarily through four government-supported programs: the Key Technologies R&D Program of China, the National Basic Research Program of China, the National High-tech R&D Program of China, and the National Natural Science Foundation of China. The key R&D activities for the development of new wrought magnesium alloys in China are reviewed, and typical properties of some new alloys are summarized. More attentions are paid to high-strength wrought magnesium alloys and high-plasticity wrought magnesium alloys. Some novel plastic processing technologies, emerging in recent years, which aim to control deformation texture and to improve plasticity and formability especially at room temperature, are also introduced.

关键词: wrought magnesium alloy;microstructure;properties;alloy designing;plastic deformation;research projects;y-zr alloys;mechanical-properties;mg-4y-4sm-0.5zr alloy;grain-refinement;rare-earth;microstructure;gd;phase;temperature;evolution

Recent developments in high temperature intermetallics research in China

Intermetallics

A comprehensive survey was made of various advances of intermetallics research in China. The investigation focussed on the fundamental research and materials development. Charge density distribution and site occupancy of alloying elements, environmental embrittlement and chemical reaction, interface structures and phase transformation at the atomic scale, nanocrystalline intermetallics and its thermal stability, superplastic behavior and anomalous yield strength peak are reviewed. Several Ti-Al and Ni-Al based alloys have been manufactured, and show good mechanical properties. Diverse components have been fabricated successfully. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词: aluminides, miscellaneous;hydrogen embrittlement;mechanical properties;at high temperatures;superplastic behavior;phase interfaces;grain-boundary fracture;in-situ composites;environmental;embrittlement;hydrogen embrittlement;ni3al;compression;alloys;co3ti;boron;feal

(alpha-PbO2-type nanophase of TiO2 from coesite-bearing eclogite in the Dabie Mountains, China

American Mineralogist

A natural high-pressure phase of titanium oxide with alpha-PbO2-structure has been found in omphacite from coesite-bearing eclogite at Shima in the Dabie Mountains, China. High-resolution transmission electron microscope observations have revealed an orthorhombic lattice, corresponding to alpha-PbO2-type TiO2, with cell parameters a = 0.461 nm, b = 0.540 nm, c = 0.497 nm and space group Pbcn. It occurs as nanometer-thick (< 2 nm) lamellae between multiple twinned rutile crystals, providing additional evidence of very high-pressure, metamorphism at 7 GPa, 900 degrees C. This implies subduction of continental material to a depth of more than 200 kilometers. alpha-PbO-type TiO2 could be an extremely useful index mineral for ultrahigh-pressure.

关键词: high-pressure phase;ries crater;rutile;polymorph;titanium

STATISTICAL EVALUATION OF CRITICAL INCLUSION FACTOR FOR SECONDARY RECRYSTALLIZATON IN 3%Si STEEL Lecturer,Department of Materials Engineering,Southwestern Jiaotong University,Chengdu 610031,China

LI Shuchen Southwestern Jiaotong University , Chengdu , ChinaCHEN Mengzhe KE Jun University of Science and Technology Beijing , Beijing , China

金属学报(英文版)

On the basis of statistical data of MnS in the conventional 3% Si steel sheeets after various annealing processes,the critical inclusion factor has been evaluated to be 20 mm~(-1).The inhi- bition of MnS to grain growth has been exactly described.

关键词: 3%Si steel , null , null

CORRELATION BETWEEN STRESS COMPONENTS AND STRESS CORROSION CRACKS IN BRASS Lecturer,Department of Materials Physics,University of Science and Technology Beijing,Beijing 100083,China

QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing , Beijing , China

金属学报(英文版)

The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.

关键词: stress corrosion cracking , null , null , null

TEM and HRTEM study of microstructures in omphacite from UHP eclogites at Shima, Dabie Mountains, China

Acta Geologica Sinica-English Edition

Transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM) analyses have been performed on omphacite from ultra-high pressure (UHP) eclogites at the locality of Shima, Dabie Mountains, China. TEM reveals that the microstructures consist dominantly of dislocation substructures, including free dislocations, loops, tiltwalls, dislocation tangles and subboundaries. They were produced by high-temperature ductile deformation, of which the main mechanism was dislocation creep. Antiphase domain (APD) boundaries are common planar defects; an age of 470 +/- 6 Ma for UHP eclogite formation has been obtained from the equiaxial size of APDs in ordered omphacites from Shima, coincident with ages given by single-zircon U-Pb dating (471 +/- 2 Ma). HRTEM reveals C2/c and P2/n space groups in different parts of one single omphacite crystal, and no exsolution is observed in the studied samples, which is attributed to rapid cooling. It is suggested that the UHP eclogites underwent a long period of annealing at high temperatures, followed by relatively rapid cooling. These data provide valuable information for the formation and exhumation mechanism of UHP eclogites in the Dabie high-pressure (HP) and UHP metamorphic belt.

关键词: UHP eclogite;omphacite;TEM and HRTEM;Dabie mountains;high-temperature deformation;naturally deformed omphacites;diopside;single-crystal;dislocation glide;transformation;consequences;mechanisms;rocks;shan

Recent Advances of Laser Coating Technology in China

LIANG Yong LI Ruiguo Institute of Metal Research , Academia Sinica , Shenyang 110015 , ChinaInstitute of Corrosion and Protection of Metals , Aademia Sinica , Shenyang , 110015 , China

材料科学技术（英文）

Recent advances in laser coating technology including laser cladding,laser surface alloying and laser vapour deposition in China are reviewed in this paper.

关键词: laser , null , null , null , null